JP2022174485A - Method and device for measuring concentration of cellulose nanofiber in semi-permeable membrane, and method for manufacturing semi-permeable composite membrane - Google Patents

Abstract

To provide a method for measuring the concentration of cellulose nanofiber in a semi-permeable membrane with a non-destructive and simple method.SOLUTION: For a semi-permeable composite membrane obtained by providing, on a porous support formed of polysulfone, a semi-permeable membrane containing cellulose nanofiber in a concentration of more than 0 mass% and 30 mass% or less, a measuring method measures the concentration of cellulose nanofiber in the semi-permeable membrane. The measuring method includes a calibration curve creation step, an analysis step, and a calculation step. The calibration curve creation step includes determining, for a sample of the semi-permeable composite membrane including cellulose nanofiber, the concentration of cellulose nanofiber in the semi-permeable membrane based on the amount of at least aromatic polyfunctional amine and cellulose nanofiber used for preparation of the sample, irradiating with an infrared ray from the semi-permeable membrane side to analyze in advance an infrared absorption spectrum related to the porous support, and creating a calibration curve indicating the correspondence relationship between the concentration of cellulose nanofiber and the infrared absorption spectrum.SELECTED DRAWING: Figure 7

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for measuring the concentration of cellulose nanofibers in a semipermeable membrane, and a method for producing a semipermeable composite membrane.

An invention of a semipermeable composite membrane containing cellulose nanofibers and a method for producing the same has been proposed (Patent Document 1). Since it is difficult to measure the concentration of cellulose nanofibers in the semipermeable membrane, in Patent Document 1, based on the amount of cellulose nanofibers in the solution used when producing the semipermeable composite membrane, The concentration of cellulose nanofibers is calculated.

International Publication No. 2019/235441A1

However, it is currently difficult to measure the concentration of cellulose nanofibers in manufactured semipermeable membranes.

Accordingly, an object of the present invention is to provide a method and apparatus for measuring the concentration of cellulose nanofibers in a semipermeable membrane and a method for producing a semipermeable composite membrane by a simple non-destructive method.

The present invention has been made to solve at least part of the above problems, and can be implemented as the following aspects or application examples.

[1] One aspect of the method for measuring the concentration of cellulose nanofibers in a semipermeable membrane according to the present invention is
A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A method of measuring concentration, comprising:
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is a calibration curve creating step of preliminarily analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the side and creating a calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum;
an analysis step of irradiating the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side to analyze the infrared absorption spectrum of the porous support;
a calculation step of calculating the concentration of cellulose nanofibers contained in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained in the analysis step;
characterized by comprising

[2] In one aspect of the measurement method,
In the calibration curve creation step, ^the correspondence relationship is the concentration of cellulose nanofibers and 1237 cm ^{−1 ±}
at least one of a first absorption peak within 10 cm ⁻¹ , a second absorption peak within 1148 cm ⁻¹ ±10 cm ⁻¹ , and a third absorption peak within 1104 cm ⁻¹ ±10 cm ⁻¹ is the relationship between the intensity ratios of the two absorption peaks, and
In the calculating step, from the infrared absorption spectrum obtained in the analyzing step, the intensity ratio of at least one of the first absorption peak, the second absorption peak and the third absorption peak to the reference absorption peak is calculated. The concentration of cellulose nanofibers can be calculated based on the calibration curve obtained.

[3] One aspect of the measuring device according to the present invention is
A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A measuring device for measuring concentration,
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is A memory storing a calibration curve indicating the correspondence between the concentration of cellulose nanofibers and the infrared absorption spectrum, which is obtained by irradiating infrared rays from the side and analyzing the infrared absorption spectrum of the porous support in advance. Department and
an analysis unit that irradiates the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side and analyzes the infrared absorption spectrum of the porous support;
a calculation unit that calculates the concentration of cellulose nanofibers in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained by the analysis unit;
characterized by comprising

[4] One aspect of the method for producing a semipermeable composite membrane according to the present invention is
Forming a semipermeable membrane containing cellulose nanofibers on a porous support made of polysulfone,
With respect to the semipermeable composite membrane in which the semipermeable membrane is formed on the porous support, the concentration of the cellulose nanofibers in the semipermeable membrane is measured according to the above measuring method,
A semipermeable composite membrane having a predetermined concentration of cellulose nanofibers is obtained.

According to one aspect of the measuring method of the present invention, the concentration of cellulose nanofibers in a semipermeable membrane can be measured by a simple non-destructive method. Moreover, according to the measuring device of the present invention, the concentration of cellulose nanofibers in the semipermeable membrane can be measured by a simple non-destructive method. Furthermore, according to the method for producing a semipermeable composite membrane of the present invention, a semipermeable composite membrane in which the concentration of cellulose nanofibers has been measured can be produced.

1 is a longitudinal sectional view schematically showing a semipermeable composite membrane; FIG. It is a flow chart explaining a measuring method concerning one embodiment. 1 is a block diagram showing the overall configuration of a measuring device used in a measuring method according to one embodiment; FIG. 1 is a schematic illustration of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR); FIG. FIG. 2 shows infrared absorption spectra of a sample of a semipermeable composite membrane containing cellulose nanofibers and an infrared absorption spectrum of a sample of a semipermeable composite membrane containing no cellulose nanofibers. FIG. 4 is a diagram showing the relationship between the concentration of cellulose nanofibers and the intensity ratio of the first absorption peak. FIG. 4 is a diagram showing the relationship between the concentration of cellulose nanofibers and the intensity ratio of the first absorption peak using a regression line obtained by the least squares method. FIG. 4 is a diagram showing the relationship between the concentration of cellulose nanofibers and the intensity ratio of the second absorption peak by a regression line obtained by the method of least squares. FIG. 4 is a graph showing the relationship between the concentration of cellulose nanofibers and the intensity ratio of the third absorption peak using a regression line obtained by the method of least squares.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the scope of the invention described in the claims. Moreover, not all the configurations described below are essential constituent elements of the present invention.

One aspect of the method for measuring the concentration of cellulose nanofibers in the semipermeable membrane according to the present embodiment is that the concentration of cellulose nanofibers is more than 0% by mass and 30% by mass or less on a porous support made of polysulfone. A method for measuring the concentration of cellulose nanofibers in a semipermeable composite membrane provided with a semipermeable membrane, comprising: a sample of a semipermeable composite membrane containing cellulose nanofibers; The concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used, and the infrared absorption spectrum of the porous support is obtained by irradiating infrared rays from the semipermeable membrane side. A calibration curve creation step of analyzing in advance and creating a calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum, and the semipermeable composite membrane to be analyzed is irradiated with infrared rays from the semipermeable membrane side. An analysis step of analyzing the infrared absorption spectrum of the porous support, and from the infrared absorption spectrum obtained in the analysis step, based on the calibration curve, the cellulose nanofibers contained in the semipermeable membrane to be analyzed. and a calculating step of calculating the concentration.

A. Semipermeable Composite Membrane FIG. 1 is a longitudinal sectional view schematically showing a semipermeable composite membrane 100 .

A semipermeable composite membrane 100 comprises a semipermeable membrane 104 provided on a porous support 102 . The porous support 102 is covered with a semipermeable membrane 104 on at least one side. The semipermeable membrane 104 includes a crosslinked polyamide 120 (an example of crosslinked aromatic polyamide will be described below, but not limited thereto) and cellulose nanofibers 110 . The surface 105 of the semipermeable membrane 104 is entirely covered with a crosslinked aromatic polyamide 120 . The semipermeable composite membrane 100 can reduce the environmental load by including the cellulose nanofibers 110 .

Semipermeable membrane 104 comprises cellulose nanofibers 110 in crosslinked aromatic polyamide 120 . The semipermeable membrane 104 has a matrix of the crosslinked aromatic polyamide 120 , and the space between adjacent defibrated cellulose nanofibers 110 is filled with the crosslinked aromatic polyamide 120 . The presence of the cellulose nanofibers 110 can be detected by analyzing the semipermeable membrane 104 using a scanning transmission electron microscope (STEM).

In the present invention, “cellulose nanofibers” refer to natural cellulose fibers and/or oxidized cellulose fibers that have been unraveled to the nano-size level, and in particular, the average fiber diameter can be 3 nm to 200 nm, and further 3 nm. ˜150 nm, in particular cellulose microfibrils and/or cellulose microfibril bundles of 3 nm to 100 nm. That is, the cellulose nanofiber 110 can include a single cellulose nanofiber or a bundle of multiple single cellulose nanofibers. In this specification, the numerical range indicated by "-" includes an upper limit and a lower limit.

The average aspect ratio (fiber length/fiber diameter) of the cellulose nanofibers 110 can be 10-1000, more preferably 10-500, and particularly 100-350.

The thickness of the semi-permeable film 104 can be 10 nm or more and 200 nm or less, and further can be 10 nm or more and 150 nm or less. If the thickness of the semipermeable membrane 104 is 10 nm or more, it becomes possible to reinforce the semipermeable membrane 104 with cellulose nanofibers 110 that are thinner than the membrane thickness, for example, with a fiber diameter of about 3 nm. If the thickness of the semipermeable membrane 104 is 150 nm or less, it is presumed that a practical water permeation flux can be obtained when the semipermeable membrane 104 is used as the semipermeable membrane.

Since the semipermeable composite membrane 100 has excellent pressure resistance due to the reinforcing effect of the cellulose nanofibers 110, it can be used even under relatively high operating pressures. Being able to increase the operating pressure contributes to increasing the water permeation flux when the semipermeable membrane 104 is used as the semipermeable membrane. In addition, it is presumed that the use of the semipermeable membrane 104 containing the cellulose nanofibers 110 improves the anti-fouling property of the semipermeable composite membrane 100 compared to a composite membrane using a semipermeable membrane of aromatic polyamide alone. .

A porous support 102 is provided to give mechanical strength to the semipermeable membrane 104 . The porous support 102 may have substantially no separation capability.

As the porous support 102, a known porous support of a semipermeable composite membrane can be applied. For example, a porous support described in Japanese Patent No. 5120006 can be employed.

The thickness of the porous support 102 can be from 10 μm to 200 μm, preferably from 30 μm to 100 μm. The porous support 102 may have either a symmetrical structure or an asymmetrical structure, but may have an asymmetrical structure in order to achieve both the support function of the thin film and the liquid permeability.

The porous support 102 has fine pores from the front surface to the back surface. The average pore size of the side surface of the porous support 102 on which the semipermeable membrane 104 is formed can be 0.1 nm or more and 100 nm or less, and most of the side surface can have a diameter of several tens of nm or less. The porous support 102 may be reinforced with a woven fabric, non-woven fabric, or the like.

The concentration of cellulose nanofibers 110 in semipermeable membrane 104 is more than 0% by mass and 30% by mass or less. If the concentration is 30% by mass or less, the measurement method according to the present embodiment can be applied, and in particular, it is difficult to produce a homogeneous semipermeable membrane 104 with a concentration exceeding 30% by mass. A range of possible semipermeable membrane 104 concentrations can be covered. Further, for example, the concentration of the cellulose nanofibers 110 in the semipermeable membrane 104 is preferably 0.2% by mass or more and 18% by mass or less, more preferably 0.3% by mass or more and 18% by mass or less, Furthermore, it is preferable that it is 0.35 mass % or more and 18 mass % or less. If the content of the cellulose nanofibers 110 is 0.2% by mass or more, a higher water permeability can be obtained than a semipermeable membrane made of aromatic polyamide alone. If the content of the cellulose nanofibers 110 is 0.2% by mass or more, the arithmetic mean height (Sa) of the semipermeable membrane 104 is small, so the organic fouling resistance is improved compared to the semipermeable membrane of aromatic polyamide alone. You can guess. According to experiments by the present inventors, when the content of cellulose nanofibers 110 is 18% by mass or less, the aqueous dispersion of cellulose nanofibers can be easily applied, and the semipermeable composite membrane 100 can be easily manufactured. The content of the cellulose nanofibers 110 in the semipermeable membrane 104 is obtained from the interfacial polymerization reaction formula. A method for measuring the content will be described later.

Examples of types of solutions separated by the semipermeable composite membrane 100 include highly concentrated brine, seawater, and concentrated seawater.

Semipermeable composite membranes can be used by incorporating them into, for example, spiral, tubular, and plate-and-frame elements, and hollow fibers can be bundled and incorporated into elements.

Regarding the semipermeable composite membrane 100, the restoration of the water permeation flux that has been reduced due to fouling will be described later.

B. Raw Materials First, each raw material used in the method for producing a semipermeable composite membrane will be described.

B-1. Cellulose nanofibers Cellulose nanofibers are natural cellulose fibers and/or oxidized cellulose fibers that have been unraveled to the nano-size level, and in particular, the average fiber diameter can be 3 nm to 200 nm, and more preferably 3 nm to 150 nm. cellulose microfibrils and/or cellulose microfibril bundles from 3 nm to 100 nm. That is, the cellulose nanofiber can include a single cellulose nanofiber or a bundle of a plurality of single cellulose nanofibers.

The average aspect ratio (fiber length/fiber diameter) of the cellulose nanofibers may be 10-1000, more preferably 10-500, particularly 100-350.

Cellulose nanofibers are provided as a cellulose nanofiber aqueous dispersion. The aqueous dispersion may contain oxidized cellulose fibers. Cellulose nanofibers are biomass made from pulp such as wood, and effective use of cellulose nanofibers is expected to reduce environmental impact.

B-2. Method for Producing Aqueous Dispersion of Cellulose Nanofibers An aqueous dispersion containing cellulose nanofibers includes, for example, an oxidation step of oxidizing natural cellulose fibers to obtain oxidized cellulose fibers, and a refining step of refining the oxidized cellulose fibers. It can be obtained by a manufacturing method. An aqueous dispersion containing oxidized cellulose fibers can be produced, for example, by an oxidation process in which natural cellulose fibers are oxidized to obtain oxidized cellulose fibers.

First, in the oxidation step, water is added to natural cellulose fibers as a raw material and treated with a mixer or the like to prepare slurry in which natural cellulose fibers are dispersed in water. Here, the natural cellulose fibers include, for example, wood pulp, cotton pulp, bacterial cellulose, and the like. More specifically, examples of wood pulp include softwood pulp and hardwood pulp, examples of cotton pulp include cotton linter and cotton lint, and examples of non-wood pulp include: Straw pulp, bagasse pulp and the like can be mentioned. At least one of these can be used as the natural cellulose fiber.

Natural cellulose fibers have a structure composed of bundles of cellulose microfibrils with lignin and hemicellulose filling the spaces between them. That is, it is presumed to have a structure in which cellulose microfibrils and/or cellulose microfibril bundles are surrounded by hemicellulose and further covered by lignin. Cellulose microfibrils and/or cellulose microfibril bundles are strongly adhered by lignin to form plant fibers. Therefore, it is preferable that the lignin in the plant fibers is removed in advance in order to prevent aggregation of the cellulose fibers in the plant fibers. Specifically, the lignin content in the plant fiber-containing material is usually about 40% by mass or less, preferably about 10% by mass or less. Moreover, the lower limit of the removal rate of lignin is not particularly limited, and the closer to 0% by mass, the better. In addition, the measurement of lignin content can be measured by the Klason method.

As cellulose microfibrils, cellulose microfibrils with a fiber diameter of about 3 to 4 nm exist as the minimum unit, and this can be called a single cellulose nanofiber.

Next, in the oxidation step, the natural cellulose fibers are oxidized in water using an N-oxyl compound as an oxidation catalyst to obtain oxidized cellulose fibers. Examples of N-oxyl compounds that can be used as cellulose oxidation catalysts include 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (hereinafter also referred to as TEMPO), 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO and the like can be used.

After the oxidation step, for example, a purification step of repeating water washing and filtration can be performed to remove impurities other than the oxidized cellulose fibers contained in the slurry, such as unreacted oxidizing agents and various by-products. The solvent containing the oxidized cellulose fibers is in a state of being impregnated with water, for example, and at this stage the oxidized cellulose fibers have not been defibrated into units of cellulose nanofibers. Although water can be used as the solvent, for example, water-soluble organic solvents (alcohols, ethers, ketones, etc.) can be used in addition to water depending on the purpose.

Oxidized cellulose fibers have carboxyl groups as a result of modification of some hydroxyl groups of cellulose nanofibers with substituents having carboxyl groups.

The oxidized cellulose fibers can have an average fiber diameter of 10 μm to 30 μm. The average fiber diameter of the oxidized cellulose fibers is the arithmetic average value measured for at least 50 or more oxidized cellulose fibers within the field of view of the electron microscope.

Oxidized cellulose fibers can be bundles of cellulose microfibrils. The oxidized cellulose fibers do not need to be defibrated into cellulose nanofiber units in the later-described mixing step and drying step. Oxidized cellulose fibers can be defibrated into cellulose nanofibers in a refining process.

In the refining step, the oxidized cellulose fibers can be stirred in a solvent such as water to obtain cellulose nanofibers.

In the micronization step, water can be used as a solvent as a dispersion medium. As solvents other than water, water-soluble organic solvents such as alcohols, ethers, ketones, etc. can be used singly or in combination.

Stirring treatment in the miniaturization step includes, for example, a disaggregator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-screw extruder, a twin-screw extruder, an ultrasonic agitator, and a household juicer mixer. etc. can be used.

Further, the solid content concentration of the solvent containing the oxidized cellulose fibers in the pulverization treatment is, for example, 50
% by mass or less. If this solid content concentration is 50% by mass or less, dispersion can be achieved with a small amount of energy.

An aqueous dispersion containing cellulose nanofibers can be obtained by the micronization process. An aqueous dispersion containing cellulose nanofibers can be a colorless, transparent or translucent suspension. In the suspension, cellulose nanofibers, which are fibers that have been surface-oxidized and fibrillated to make them finer, are dispersed in water. That is, in this aqueous dispersion, cellulose nanofibers can be obtained by weakening the strong cohesive force between microfibrils (hydrogen bonds between surfaces) by introducing carboxyl groups in an oxidation process, and then undergoing a microfibrillation process. . By adjusting the conditions of the oxidation step, the carboxyl group content, polarity, average fiber diameter, average fiber length, average aspect ratio, etc. can be controlled.

The aqueous dispersion thus obtained can contain 0.1% by mass to 10% by mass of cellulose nanofibers. Alternatively, for example, it may be an aqueous dispersion of cellulose nanofibers diluted to a solid content of 1% by mass. Furthermore, the aqueous dispersion can have a light transmittance of 40% or more, and further can have a light transmittance of 60% or more, and in particular can have a light transmittance of 80% or more. The transmittance of the aqueous dispersion can be measured as the transmittance at a wavelength of 660 nm using an ultraviolet-visible spectrophotometer.

B-3. Polyamide Polyamide can be an aromatic polyamide. The polyamide in the semipermeable membrane is crosslinked. Crosslinked polyamides are obtained by interfacial polycondensation of aromatic polyfunctional amines and polyfunctional acid halides.

Aromatic polyamides contain an aromatic polyfunctional amine component. The aromatic polyamide can be a wholly aromatic polyamide. Examples of aromatic polyfunctional amines include m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4- At least one aromatic polyfunctional amine selected from the group consisting of diaminotoluene, 2,4-diaminoanisole, amidole, xylylenediamine, N-methyl-m-phenylenediamine and N-methyl-p-phenylenediamine is preferred. These may be used alone or in combination of two or more. In particular, m-phenylenediamine or 1,3,5-triaminobenzene is preferable from the viewpoint of stability of performance development.

The crosslinked aromatic polyamide can have functional groups selected from the group consisting of COO ⁻ , NH ₄ ⁺ , and COOH.

The polyfunctional acid halide is an acid halide having two or more halogenated carbonyl groups in one molecule, and is not particularly limited as long as it gives a polyamide by reaction with the polyfunctional amine. Examples of polyfunctional acid halides include oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. , 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid. Among acid halides, acid chlorides are preferred, and acid halides of 1,3,5-benzenetricarboxylic acid are particularly preferred from the viewpoints of economic efficiency, availability, ease of handling, ease of reactivity, and the like. Preferred is trimesic acid chloride (hereinafter referred to as TMC). The polyfunctional acid halides may be used singly or as a mixture of two or more.

B-4. Porous Support As the porous support 102, polysulfone, polyethersulfone, cellulose acetate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, and the like can be used. Polysulfone is suitable for the porous support 102 because it has high chemical, mechanical and thermal stability.

C. Method for Producing Semipermeable Composite Membrane Next, a method for producing a semipermeable composite membrane will be described. A method for producing a semipermeable composite membrane according to an embodiment of the present invention comprises forming a semipermeable membrane containing cellulose nanofibers on a porous support made of polysulfone, and forming a semipermeable membrane on the porous support. Regarding the formed semipermeable composite membrane, the concentration of cellulose nanofibers in the semipermeable membrane is measured by the "E. Measurement method" described later, and a semipermeable composite membrane having a predetermined concentration of cellulose nanofibers is obtained. characterized by obtaining The steps other than the measurement method in the method for producing a semipermeable composite membrane include a step of obtaining a mixed solution containing cellulose nanofibers, water and an amine component; and a step of obtaining a semipermeable composite membrane by cross-linking the amine component in the mixed solution attached to the body.

C-1. Step of obtaining a mixed solution The step of obtaining a mixed solution includes, for example, mixing a first aqueous solution containing an amine component and an aqueous dispersion of defibrated cellulose nanofibers to obtain a second aqueous solution containing an amine component and cellulose nanofibers. can include the step of obtaining The first aqueous solution contains water and an amine component. At least one of the aromatic amines described in B-2 above can be selected as the amine component. The solvent used for the first aqueous solution is preferably water. The aqueous dispersion contains water and cellulose nanofibers described in B-1 above. The second aqueous solution is obtained by mixing the first aqueous solution and the aqueous dispersion. A known method can be used for this mixing method, and for example, a magnetic stirrer, an ultrasonic stirrer, or the like can be used.

The concentration of the aromatic amine component in the second aqueous solution may be 0.5% to 5.0% by weight, and the concentration of the cellulose nanofibers 110 may be 0.01% to 0.6% by weight. If the aromatic amine in the second aqueous solution is 0.5% by mass or more, the thickness and crosslink density of the composite membrane active layer necessary for a semipermeable membrane can be formed, so that a suitable desalination rate and water permeability can be achieved. is preferable. Also, if the aromatic amine is 5.0% by mass or less, the amount of unreacted residual amine in the semipermeable membrane is small and the possibility of elution into the membrane-permeated water is low, so this range is preferred. If the cellulose nanofiber content in the second aqueous solution is less than 0.01% by mass, it becomes difficult to improve the water permeation flux, and if it exceeds 0.6% by mass, processing using the aqueous dispersion becomes difficult. Therefore, this range is preferable.

C-2. Step of Obtaining Semipermeable Composite Membrane The step of obtaining the semipermeable composite membrane 100 includes contacting the second aqueous solution obtained as described above with the porous support 102, and then the second aqueous solution adhered to the porous support 102. Aromatic amines in an aqueous solution are subjected to a cross-linking reaction.

The second aqueous solution is applied to the porous support 102 and dried. After that, a solution containing a cross-linking agent is further applied onto the second aqueous solution to cause a polycondensation reaction to cause cross-linking, dried at room temperature and then washed with distilled water to form a semipermeable membrane 104 . In this way, the semipermeable composite membrane 100 described above in "A. Semipermeable Composite Membrane" can be produced.

The step of applying the second aqueous solution to the porous support 102 can be performed uniformly using a bar coater. Any known device other than the bar coater may be employed as long as the coating can be uniformly applied.

As the cross-linking agent, for example, an organic solvent solution containing an acid chloride component such as trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, and biphenyldicarboxylic acid chloride can be used. In addition to the cross-linking agent, a basic catalyst for trapping hydrochloric acid that replicates due to interfacial polymerization is contained. Examples of the basic catalyst include triethylamine and pyridine.

Next, with regard to the semipermeable composite membrane in which the semipermeable membrane is formed on the porous support, the concentration of cellulose nanofibers in the semipermeable membrane is measured according to the "E. Measurement method" described later, and the concentration of the cellulose nanofibers is measured. to obtain a semipermeable composite membrane having a concentration of For example, using the measurement results, semipermeable composite membranes that do not meet the quality control standards are excluded based on the predetermined quality control standards, and semipermeable composite membranes that meet the quality control standards are accepted (judged as non-defective products). ). Quality control standards, for example, set an acceptable range for a given concentration of cellulose nanofibers.

D. Applications Applications of semipermeable composite membranes include, for example, seawater and brackish water desalination. Further, applications of the semipermeable composite membrane include, for example, food industry wastewater treatment, industrial process wastewater treatment, RO pretreatment of activated sludge treated water, etc., because the semipermeable membrane is excellent in contamination resistance.

The semipermeable composite membrane may be incorporated into a semipermeable composite membrane element. In the semipermeable composite membrane element, for example, between the semipermeable composite membranes stacked so that the surfaces on the semipermeable membrane side (semipermeable membrane surfaces) and the surfaces on the opposite side face each other and the surfaces on the semipermeable membrane side The permeated water flowing through the permeate-side channel formed by the raw water-side channel material provided in the permeate-side channel material, the permeate-side channel material provided between the surface on the opposite side of the semipermeable membrane, and the permeate-side channel material is collected. and a perforated water collecting pipe. That is, in the semipermeable composite membrane element, the semipermeable composite membrane, the raw water side channel material, the semipermeable composite membrane, the permeate side channel material, and the semipermeable composite membrane are stacked in this order.

The function of the semipermeable composite membrane element will be explained. While the raw water flows through the raw water channel formed between the semipermeable composite membranes by the raw water channel material, part of the raw water permeates through the semipermeable composite membranes. The permeate thus obtained has a lower solute concentration than the raw water. On the other hand, the solute in the water flowing through the raw water side channel is concentrated.

E. Measurement Method A measurement method will be described with reference to FIG. FIG. 2 is a flow chart for explaining a measuring method for measuring the concentration of cellulose nanofibers according to one embodiment.

As shown in FIG. 2, the measurement method according to the present embodiment uses a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and 30% by mass or less on a porous support made of polysulfone. A method for measuring the concentration of cellulose nanofibers in a semipermeable membrane of a permeable composite membrane, comprising a calibration curve preparation step S10, an analysis step S20, and a calculation step S30. The measurement method may further include a display step S40. In the semipermeable composite membrane, it is desirable that the cellulose nanofibers in the semipermeable membrane are dispersed throughout the semipermeable membrane in a defibrated state. This is because, in infrared spectroscopy, since infrared light is transmitted through the semipermeable membrane, accurate measurement cannot be performed if the distribution of cellulose nanofibers in the semipermeable membrane is uneven.

E-1. Calibration curve creation step In the calibration curve creation step (S10), for a sample of a semipermeable composite membrane containing cellulose nanofibers, a semipermeable membrane based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used to prepare the sample. Obtain the concentration of cellulose nanofibers inside, irradiate infrared rays from the semipermeable membrane side, analyze the infrared absorption spectrum of the porous support in advance, and determine the correspondence between the concentration of cellulose nanofibers and the infrared absorption spectrum. Prepare the calibration curve shown.

First, the concentration of cellulose nanofibers in the semipermeable composite membrane sample is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, based on Patent Document 1 (International Publication No. 2019/235441). Here, how to determine the content of the cellulose nanofibers 110 will be specifically described below using a cross-linking reaction between m-phenylenediamine and trimesic acid chloride. In the polyamide produced by the cross-linking reaction by interfacial polymerization, the two —NH ₂ groups of m-phenylenediamine and the three —COCl groups of trimesic acid chloride are not completely reacted, but partially remain. First, 3 mol of m-phenylenediamine (324.4 g) and 2 mol of trimesic acid chloride (530.9 g) are polymerized to form a polyamide (636.7 g) as shown in the following reaction formula (1). Assume.

The concentration of the cellulose nanofibers 110 (CNF content (% by mass)) in the semipermeable membrane 104 can be calculated by the following formula (1). Based on the above reaction formula (1) and the composition of the aqueous solution containing m-phenylenediamine and cellulose nanofibers, the mass of the polyamide to be produced is obtained, and then the mass of the produced polyamide is obtained, and By determining the amount of reacted m-phenylenediamine, the mass (Ma) of the polyamide actually produced can be calculated. The mass of this unreacted m-phenylenediamine can be measured by an experiment described later, and the mass of the produced polyamide can be estimated to determine the content (% by mass) of cellulose nanofibers. For combinations other than m-phenylenediamine and trimesic acid chloride, the CNF content can be determined by similarly performing mass estimation etc. by applying to each reaction formula. In the present embodiment, the concentration of cellulose nanofibers was calculated using the cross-linking reaction between m-phenylenediamine and trimesic acid chloride, but the combination of other aromatic polyfunctional amines and polyfunctional acid halides It can be similarly calculated using a reaction formula corresponding to the combination.

Next, the infrared absorption spectrum of the sample of the semipermeable composite membrane for which the concentration of cellulose nanofibers was calculated by the above method is analyzed. Analysis of the infrared absorption spectrum can be performed using an infrared spectrophotometer, and in particular, total reflection infrared spectroscopy (IR-ATR method) using a Fourier transform infrared spectrometer (FT-IR). can.

In total reflection infrared spectroscopy, a sample is brought into close contact with a prism with a high refractive index, and an absorption spectrum of the sample is obtained using an evanescent wave generated by allowing infrared light to enter the prism. In total reflection infrared spectroscopy, the depth of light reaching the sample (the depth of penetration of light) is considered to be about 0.5 μm to 2 μm. The semipermeable composite membrane, which is a sample, is brought into close contact with a prism, and infrared light is irradiated from the semipermeable membrane side, and the infrared light is reflected within the porous support. Therefore, the absorption spectrum of the sample obtained by total reflection infrared spectroscopy is the absorption spectrum of the porous support.

Research by the present inventors has revealed that the absorption spectrum of this porous support is closely related to the concentration of cellulose nanofibers in the semipermeable membrane through which infrared light is transmitted in spectroscopy. A calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum is prepared from the absorption spectrum of the porous support.

For example, when the porous support is made of polysulfone, the correspondence in the calibration ^curve is the concentration of cellulose nanofibers in the semipermeable membrane and the reference absorption ^peak (I ₀ ) in the range of 1237 cm ⁻¹ ±10 cm ⁻¹ , the second absorption peak (I ₂ ) in the range of 1148 cm ⁻¹ ± ₁₀ cm ⁻¹ and 1104 cm ⁻¹ ±10 cm and the intensity ratio (Ia=I _1,2,3 /I ₀ ) of at least one of the third absorption peaks (I ₃ ) within ⁻¹ . Therefore, the intensity ratio (Ia) may be I ₁ /I ₀ , I ₂ /I ₀ , or I ₃ /I ₀ , and I ₀ may be the average value of two or more absorption peaks ( For example, it may be divided by (I ₁ +I ₂ )/2).

The infrared absorption spectrum of polysulfone shows a peak around 1486 cm ⁻¹ , a peak around 1237 cm ⁻¹ , a peak around 1148 cm ⁻¹ and a peak around 1104 cm ⁻¹ . The reason why the infrared absorption spectrum of the semipermeable composite membrane changes depending on the concentration of cellulose nanofibers is that the cellulose nanofibers re-absorb the infrared light reflected from the polysulfone, and the re-absorption is due to the polysulfone It is presumed that there is a difference in absorption at the wavenumber (cm ⁻¹ ) of the four peaks in .

The calibration curve shows the absorption peak intensity ratio (Ia=I _1,2,3 /I ₀ ) obtained by spectroscopy and the concentration of cellulose nanofibers (at least the aromatic polyfunctional amine and cellulose nanofibers used to prepare the sample). Concentration calculated in advance based on the amount) is graphed, and a regression line can be obtained by the method of least squares. However, semipermeable membranes in which the concentration of cellulose nanofibers exceeds 30% by mass are not included in the above correspondence because the wire diameter approximation formula does not hold.

E-2. Analysis Step In the analysis step (S20), the semipermeable composite membrane to be analyzed is irradiated with infrared rays from the semipermeable membrane side to analyze the infrared absorption spectrum of the porous support.

The infrared absorption spectrum of the sample of the semipermeable composite membrane to be analyzed is analyzed in the same manner as in the calibration curve preparation step (S10). The semipermeable composite membrane sample to be analyzed is a sample in which the concentration of cellulose nanofibers in the semipermeable membrane is unknown.

In the calibration curve creation step (S10) and the analysis step (S20), the infrared absorption spectrum can be analyzed using a total reflection infrared spectrometer. As the total reflection infrared spectrometer, a commercially available device can be used, for example, Nicolet 6700 FT-IR device manufactured by Thermo Scientific.

E-3. Calculation step In the calculation step (S30), the concentration of cellulose nanofibers contained in the semipermeable membrane to be analyzed is calculated from the infrared absorption spectrum obtained in the analysis step (S20) based on the calibration curve.

For example, when _the porous support is polysulfone, ^from the infrared absorption spectrum obtained by the analysis ^step ( ^S20 ), there is A first absorption peak (I ¹ ) within the range of ±10 cm ₋₁ , a second absorption peak (I ₂ ) within the range of 1148 cm ⁻¹ ±10 cm ⁻¹ and within the range of 1104 cm ⁻¹ ±10 cm ⁻¹ Determine the intensity ratio (Ib=I _1,2,3 /I ₀ ) of at least one absorption peak of the third absorption peak (I ₃ ) at , and based on the calibration curve obtained in the calibration curve creation step (S10) Then, the concentration of cellulose nanofibers is calculated. That is, if the absorption peak intensity ratio (Ib) of the analysis target is obtained, the concentration of cellulose nanofibers corresponding to the absorption peak intensity ratio (Ia) in the calibration curve can be calculated. The intensity ratio (Ib) may be, for example, I ₁ /I ₀ , I ₂ /I ₀ , I ₃ /I ₀ , or I ₀ in accordance with the calibration curve. It may be divided by the average value of absorption peaks (eg (I ₁ +I ₂ )/2).

E-4. Display Step In the display step (S40), the concentration of cellulose nanofibers in the semipermeable membrane calculated in the calculation step (S30) is displayed, for example, on a display.

F. Measuring Device A measuring device for measuring the concentration of cellulose nanofibers in the semipermeable membrane will be described with reference to FIG. FIG. 3 is a block diagram showing the overall configuration of a measuring device 1 for measuring the concentration of cellulose nanofibers according to one embodiment.

As shown in FIG. 3, the measuring device 1 according to the present embodiment has a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and 30% by mass or less on a porous support made of polysulfone. A measuring device 1 for measuring the concentration of cellulose nanofibers in a semipermeable composite membrane, comprising an analysis unit 20, a calculation unit 30, and a storage unit 40. As the measuring device 1, a computer that can execute the processing of each part can be adopted.

The measuring device 1 may further include an input section 10 . The input unit 10 may include a known input device such as a keyboard.

The measuring device 1 may further include a display section 50 . The display unit 50 can display the analysis result by the analysis unit 20 and the calculation result by the calculation unit 30, for example. The display unit 50 can employ a known display device such as a display.

The storage unit 40 stores a sample of a semipermeable composite membrane containing cellulose nanofibers, based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used to prepare the sample, and stores the concentration of cellulose nanofibers in the semipermeable membrane. A calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum obtained by preliminarily analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the semipermeable membrane side is obtained. remembered. The calibration curve can be obtained according to the above “E-1. Calibration curve preparation step”.

The analysis unit 20 irradiates the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side to analyze the infrared absorption spectrum of the porous support. The analysis unit 20 may be a part of the spectroscopic device, or may analyze based on the output from the spectroscopic device. The analysis unit 20 is, for example, a computer or the like. The analysis unit 20 can execute the process described in "E-2. Analysis step" above.

The calculation unit 30 calculates the concentration of cellulose nanofibers in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained by the analysis unit 20 . The calculator 30 may be a computer built into or connected to the spectroscopic device. The calculation unit 30 can execute the processing described in "E-3. Calculation step" above.

As used herein and in the claims, "at least one of A, B and C" or "one or more of A, B and C" in relation to a listing of one or more elements is , A only, B only, C only, the set of A and B, the set of A and C, the set of B and C, the set of A, B and C, and so on.

The present invention may omit a part of the configuration or combine each embodiment and modifications as long as the features and effects described in the present application are provided.

The present invention includes configurations that are substantially the same as the configurations described in the embodiments (configurations that have the same function, method and result, or configurations that have the same purpose and effect). Moreover, the present invention includes configurations obtained by replacing non-essential portions of the configurations described in the embodiments. In addition, the present invention includes a configuration that achieves the same effects or achieves the same purpose as the configurations described in the embodiments. In addition, the present invention includes configurations obtained by adding known techniques to the configurations described in the embodiments.

Examples of the present invention will be described below, but the present invention is not limited to these.

Examples of the present invention will be described below, but the present invention is not limited to these.

(1) Preparation of sample 1 (CNF 1.26% by mass)
(1-1) Preparation of Porous Support Made of a mixed yarn of a polyester fiber with a single yarn fineness of 0.5 decitex and a polyester fiber with a single yarn fineness of 1.5 decitex, air permeability of 0.7 cm ³ /cm ² ·sec, average A wet-laid non-woven fabric having a pore size of 7 μm or less and a size of 30 cm long and 20 cm wide was fixed on a glass plate, and a solution of dimethylformamide (DMF) solvent with a polysulfone concentration of 15% by weight (20 ° C. ) was cast to a total thickness of 210 μm to 215 μm and immediately immersed in water to produce a polysulfone porous support.

(1-2) Preparation of second aqueous solution A first aqueous solution obtained by adding 50 g of distilled water to 6 g of m-phenylenediamine and stirring and mixing using a magnetic stirrer, and water having a cellulose nanofiber concentration of 0.6% by mass. 5 g of the dispersion liquid was stirred and mixed using a magnetic stirrer, and additives (SLS (sodium lauryl sulfate) 0.45 g, CSA (camphorsulfonic acid) 12 g, TEA (triethylamine) 6 g, IPA (Isopropyl alcohol) 18 g) was added, distilled water was added to make the total amount 300 g, and the mixture was stirred using a magnetic stirrer to obtain a second aqueous solution. The second aqueous solution contains 2.0% by weight of m-phenylenediamine, 0.01% by weight of cellulose nanofibers, 0.15% by weight of SLS, 4.0% by weight of CSA, 2.0% by weight of TEA, and 6.0% by weight of IPA. The average fiber diameter of cellulose nanofibers is 3 nm to 4 nm.

(1-3) Preparation of Semipermeable Composite Membrane Using a bar coater (#20 wired bar), a porous support of 80 cm ² was coated with the second aqueous solution on the surface of the porous support at a speed of 10 mm/s. After removing excess aqueous solution from the surface of the porous support with a rubber blade, 2 ml of a room temperature IP solvent solution containing 0.18% by mass of trimesic acid chloride was applied so that the membrane surface was completely wetted. In order to remove excess solution from the membrane, the membrane surface was held vertically to drain, then dried in a constant temperature bath at 120 ° C. for 3 minutes, and then immersed and washed in distilled water. ~8 semipermeable composite membranes were obtained.

(1-4) Estimation of Cellulose Nanofiber Content The cellulose nanofiber content in the semipermeable membrane was estimated from the following reaction formula (1) and an experiment to determine the amount of unreacted m-phenylenediamine.

In the above reaction formula (1), 3 mol of m-phenylenediamine (324.4 g) and 2 mol of trimesic acid chloride (530.9 g) are polymerized to produce polyamide (636.7 g). is produced from 0.51 g of m-phenylenediamine.

As a specific estimation procedure, first, it was assumed that the total amount of m-phenylenediamine applied was interfacially polymerized according to the above reaction formula (1). The amount of cellulose nanofibers relative to the total amount of m-phenylenediamine applied was calculated from the ratio of the concentrations of m-phenylenediamine and cellulose nanofibers in the second aqueous solution. Next, the ratio of unreacted m-phenylenediamine was determined by experiment to calculate the m-phenylenediamine actually interfacially polymerized, and the cellulose nanofiber content (% by mass) was calculated. CSA melts and flows out during the measurement of the water permeation flux, which will be described later, so it does not affect the calculation of the cellulose nanofiber content.

Specifically, the mass a of unreacted m-phenylenediamine in m-phenylenediamine coated from the following formula (2) by the same procedure as in the examples disclosed in Patent Document 1 (WO2019/235441A1) is asked.

Next, this sample was immersed in chloroform for a short period of time to dissolve the porous support and obtain a polyamide membrane. This film was dried at 150° C. and then weighed to obtain the mass b of the polyamide film. Since 1 g of polyamide is produced from 0.51 g of m-phenylenediamine, mass b was multiplied by 0.51 to obtain m-phenylenediamine converted mass c (0.51×mass b). The ratio d of unreacted m-phenylenediamine was determined by the following formula (3).

The cellulose nanofiber content was determined by the ratio of the mass of cellulose nanofibers to the mass of polyamide containing cellulose nanofibers. Even if the ends of the coated cellulose nanofibers enter the pores of the porous support, they do not enter the deep part of the porous support and the entire amount of the coated cellulose nanofibers exists in the surface layer. Then, the mass of the cellulose nanofibers was calculated from the concentration of the cellulose nanofibers, and this was defined as the mass e.

Regarding the mass of the polyamide produced, the mass of the polyamide produced when the total amount of the applied m-phenylenediamine is interfacially polymerized is defined as mass f, and m-phenylenediamine when the coating liquid thickness of the second aqueous solution is 15 μm. was calculated from its concentration. Assuming that the mass of the polyamide actually produced is mass h, mass h becomes smaller than mass f due to unreacted m-phenylenediamine. Since the total amount of m-phenylenediamine applied can be considered as the sum of mass a and mass c, mass h was determined by the following formula (4).

The ratio d varies depending on the conditions for preparing the semipermeable membrane, such as the concentration of m-phenylenediamine in the second aqueous solution and the concentration of cellulose nanofibers. . Using this mass h, the concentration of cellulose nanofibers (CNF concentration) (% by mass) in the semipermeable membrane was determined by the following formula (1).

The average concentration of cellulose nanofibers in the semipermeable composite membrane of sample 1 was 1.26% by mass.

(2) Preparation of samples 0, 2 to 8 Samples 0, 2 to 8 were prepared in the same manner as sample 1 by changing the amount of cellulose nanofiber in the "second aqueous solution" in (1-2) above, The concentration of cellulose nanofibers was calculated in the same manner as for sample 1. Table 1 shows the average concentration of cellulose nanofibers in the semipermeable membranes of samples 0 to 8 (“concentration of CNF (% by mass)”).

(3) Infrared spectroscopy Infrared spectroscopy was performed using a Nicolet 6700 FT-IR device 22 from Thermo Scientific. FIG. 4 is a schematic illustration of attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) in this FT-IR device 22. As shown in FIG. As shown in FIG. 4, the FT-IR device 22 comprises a reflecting prism 23, an infrared laser light source 24, and an infrared detector 25. As shown in FIG. The samples of the semipermeable composite film 100 of samples 1 to 7 are brought into close contact with the diamond prism (reflecting prism 23) of the FT-IR device 22, and the infrared beam 26 from the infrared laser light source 24 is irradiated from the semipermeable film 104 side. Attenuated total reflection was performed on the porous support 102 . The infrared detector 25 received the reflected light from the porous support 102 . The infrared beam 26 had a diameter of about 2 mm and an incident angle of 45 degrees. The measurement wavelength was 650-4500 cm ⁻¹ and the resolution was 2 cm ⁻¹ . The sample size of the semipermeable composite membrane 100 was about 1 cm square.

FIG. 5 shows the results of infrared spectroscopy of sample 0 containing no cellulose nanofibers (solid line) and sample 5 containing cellulose nanofibers (27.65% by mass) (dotted line). FIG. 5 is a diagram showing the concentration dependence of the absorption spectrum of cellulose nanofibers obtained by Fourier transform infrared spectroscopy. In FIG. 5, the vertical axis is the absorbance (arbitrary unit) and the horizontal axis is the wave number (cm ⁻¹ ). Samples 0 and 5 all exhibited absorption peaks due to polysulfone absorption near 1486 ⁻¹ cm, 1237 ⁻¹ cm, 1148 ⁻¹ cm and 1104 ⁻¹ cm. Then, when the peak intensity of the absorption peak near 1486 ^-1 cm in sample 0 and sample 5 is 1, the absorption peaks of sample 5 near 1237 ^-1 cm, near 1148 ^-1 cm and near 1104 ^-1 cm are A value smaller than each absorption peak of 0 was shown. In the same manner, the peak intensities of absorption peaks of samples 1 to 4 and 6 to 8 in infrared spectroscopy were measured.

(4) Preparation of calibration curve From the results of infrared spectroscopy, the reference absorption peak (I ₀ ), which is the peak intensity (maximum value) within the range of 1485 ^-1 cm ± 10 cm ^-1 in each sample, and 1237 cm ^-1 A first absorption peak (I ¹ ) within the range of ±10 cm ₋₁ , a second absorption peak (I ₂ ) within the range of 1148 cm ⁻¹ ±10 cm ⁻¹ and within the range of 1104 cm ⁻¹ ±10 cm ⁻¹ Find the intensity ratio (Ia=I ₁ /I ₀ , Ia=I ₂ /I ₀ , Ia=I ₃ /I ₀ ) with each peak intensity (maximum value) of the third absorption peak (I ₃ ) at rice field. Baseline subtraction was not performed when determining the absorption peak intensity ratio (Ia).

Since the concentration of cellulose nanofibers in each sample was calculated in (1) and (2) above, the correspondence relationships shown in FIGS. 6 to 9 were determined based on the peak intensity ratio (Ia). In FIGS. 6 to 9, “●” indicates the average value of the peak intensity ratio at each cellulose nanofiber concentration, and “−” indicates the minimum and maximum values of the peak intensity ratio at each cellulose nanofiber concentration. 6 and 7 are diagrams showing the relationship between the concentration of cellulose nanofibers and the intensity ratio (Ia=I ₁ /I _{0 ) of the first absorption peak (I 1 )} to the reference absorption peak (I ₀ ). 8 is a diagram showing the relationship between the concentration of cellulose nanofibers and the intensity ratio (Ia=I ₂ /I ₀ ) of the second absorption peak (I ₂ ) to the reference absorption peak (I ₀ ), and FIG. FIG. 4 is a diagram showing the relationship between the concentration of nanofibers and the intensity ratio (Ia= _{I 3 /} I ₀ ) of the third absorption peak (I ₃ ) to the reference absorption peak (I 0 ). 6 to 9, the vertical axis is the peak intensity ratio (Ia), and the horizontal axis is the concentration (% by mass) of cellulose nanofibers in the semipermeable membrane.

As shown in FIG. 6, when the concentration of cellulose nanofibers in samples 6 to 8 exceeds 30% by mass, the peak intensity ratio (Ia) is clearly different from that in samples 0 to 5. Therefore, samples 6 to 8 A regression line was obtained by the least squares method for the average values of the peak intensity ratios (Ia) when the cellulose nanofiber concentration was 0% by mass to 27.65% by mass (samples 0 to 5), and the calibration curve ( indicated by a solid line). Similarly to FIG. 7, the second absorption peak and the third absorption peak are also shown in FIGS. 8 and 9 from the peak intensity ratio (Ia) when the concentration of cellulose nanofibers is 0% by mass to 27.65% by mass. Indicated.

(5) Measurement of cellulose nanofiber concentration A peak obtained by infrared spectroscopic analysis of a polysulfone porous support for a semipermeable composite membrane sample with an unknown cellulose nanofiber concentration in the same manner as samples 0 to 5. From the intensity ratio (Ib), the concentration of cellulose nanofibers can be calculated based on the calibration curves of FIGS. 7 and 8, and the concentration of cellulose nanofibers contained in the sample of the semipermeable membrane to be analyzed can be measured. .

Reference Signs List 1 measuring device 10 input unit 20 analysis unit 22 FT-IR device 23 reflecting prism 24 infrared laser light source 25 infrared detector 26 infrared beam 30 calculation unit 40 Memory part 50 Display part 100 Semipermeable composite membrane 102 Porous support 104 Semipermeable membrane 105 Surface 110 Cellulose nanofiber 120 Crosslinked aromatic polyamide

[1] One aspect of the method for measuring the concentration of cellulose nanofibers in a semipermeable membrane according to the present invention is
A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A method of measuring concentration, comprising:
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is a calibration curve creating step of preliminarily analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the side and creating a calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum;
an analysis step of irradiating the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side to analyze the infrared absorption spectrum of the porous support;
a calculation step of calculating the concentration of cellulose nanofibers contained in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained in the analysis step;
including
In the calibration curve creation step, the correspondence relationship is the concentration of cellulose nanofibers and the first absorption within the range of 1237 cm ⁻¹ ±10 cm ⁻¹ with respect to the reference absorption peak within the range of 1486 cm ⁻¹ ±10 cm ⁻¹ a second absorption peak within the range of 1148 cm ⁻¹ ±10 cm ⁻¹ and a third absorption peak within the range of 1104 cm ⁻¹ ±10 cm ⁻¹
the intensity ratio of at least one absorption peak of the peak, and
In the calculating step, from the infrared absorption spectrum obtained in the analyzing step, the intensity ratio of at least one of the first absorption peak, the second absorption peak and the third absorption peak to the reference absorption peak is calculated. The concentration of cellulose nanofibers is calculated based on the calibration curve .

[2] One aspect of the method for producing a semipermeable composite membrane according to the present invention is
Forming a semipermeable membrane containing cellulose nanofibers on a porous support made of polysulfone,
With respect to the semipermeable composite membrane in which the semipermeable membrane is formed on the porous support, the concentration of the cellulose nanofibers in the semipermeable membrane is measured according to the above measuring method,
A semipermeable composite membrane having a predetermined concentration of cellulose nanofibers is obtained .

[3] One aspect of the measuring device according to the present invention is
A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A measuring device for measuring concentration,
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is A memory storing a calibration curve indicating the correspondence between the concentration of cellulose nanofibers and the infrared absorption spectrum, which is obtained by irradiating infrared rays from the side and analyzing the infrared absorption spectrum of the porous support in advance. Department and
an analysis unit that irradiates the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side and analyzes the infrared absorption spectrum of the porous support;
a calculation unit that calculates the concentration of cellulose nanofibers in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained by the analysis unit;
including
The correspondence of the calibration curve is the concentration of cellulose nanofibers and the first absorption peak within the range of 1237 cm ⁻¹ ±10 cm ⁻¹ to the reference absorption peak within the range of 1486 cm ⁻¹ ±10 cm ⁻¹ , 1148 cm −1 . A relationship between the intensity ratio of at least one absorption peak of a second absorption peak within the range of −1 ±10 cm −1 and a third absorption peak within the range of 1104 cm −1 ^{± 10 cm} −1 ^,
The calculation unit calculates an intensity ratio of at least one absorption peak of the first absorption peak, the second absorption peak, and the third absorption peak to the reference absorption peak from the infrared absorption spectrum obtained by the analysis unit. and the concentration of cellulose nanofibers is calculated based on the calibration curve .

One aspect of the method for measuring the concentration of cellulose nanofibers in the semipermeable membrane according to the present embodiment is that the concentration of cellulose nanofibers is more than 0% by mass and 30% by mass or less on a porous support made of polysulfone. A method for measuring the concentration of cellulose nanofibers in a semipermeable composite membrane provided with a semipermeable membrane, comprising: a sample of a semipermeable composite membrane containing cellulose nanofibers; The concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used, and the infrared absorption spectrum of the porous support is obtained by irradiating infrared rays from the semipermeable membrane side. A calibration curve creation step of analyzing in advance and creating a calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum, and the semipermeable composite membrane to be analyzed is irradiated with infrared rays from the semipermeable membrane side. An analysis step of analyzing the infrared absorption spectrum of the porous support, and from the infrared absorption spectrum obtained in the analysis step, based on the calibration curve, the cellulose nanofibers contained in the semipermeable membrane to be analyzed. a calculation step of calculating the concentration , and in the calibration curve creation step, the correspondence relationship is the concentration of cellulose nanofibers and 1237 cm −1 with respect to a reference absorption peak within the range of ¹⁴⁸⁶ cm ⁻¹ ±10 cm ⁻¹ At least a first absorption peak within the range of ±10 cm ⁻¹ , a second absorption peak within the range of 1148 cm ⁻¹ ±10 cm ⁻¹ , and a third absorption peak within the range of 1104 cm ⁻¹ ±10 cm ⁻¹ It is a relationship with the intensity ratio of one absorption peak, and in the calculation step, from the infrared absorption spectrum obtained by the analysis step, the first absorption peak with respect to the reference absorption peak, the second absorption peak and The intensity ratio of at least one of the third absorption peaks is obtained, and the concentration of cellulose nanofibers is calculated based on the calibration curve.

Claims (4)

A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A method of measuring concentration, comprising:
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is a calibration curve creating step of preliminarily analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the side and creating a calibration curve showing the correspondence relationship between the concentration of cellulose nanofibers and the infrared absorption spectrum;
an analysis step of irradiating the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side to analyze the infrared absorption spectrum of the porous support;
a calculation step of calculating the concentration of cellulose nanofibers contained in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained in the analysis step;
A method for measuring the concentration of cellulose nanofibers in a semipermeable membrane, comprising: In claim 1,
In the calibration curve creation step, the correspondence relationship is the concentration of cellulose nanofibers and the first absorption within the range of 1237 cm ⁻¹ ±10 cm ⁻¹ with respect to the reference absorption peak within the range of 1486 cm ⁻¹ ±10 cm ⁻¹ a peak, a second absorption peak within the range of 1148 cm ⁻¹ ±10 cm ⁻¹ , and a third absorption peak within the range of 1104 cm ⁻¹ ±10 cm ⁻¹ with an intensity ratio of at least one absorption peak. ,And,
In the calculating step, from the infrared absorption spectrum obtained in the analyzing step, the intensity ratio of at least one of the first absorption peak, the second absorption peak and the third absorption peak to the reference absorption peak is calculated. A method for measuring the concentration of cellulose nanofibers in a semipermeable membrane, wherein the concentration of cellulose nanofibers is calculated based on the calibration curve. A semipermeable composite membrane comprising a porous support made of polysulfone and a semipermeable membrane having a cellulose nanofiber concentration of more than 0% by mass and not more than 30% by mass, wherein the cellulose nanofibers in the semipermeable membrane are A measuring device for measuring concentration,
For a sample of a semipermeable composite membrane containing cellulose nanofibers, the concentration of cellulose nanofibers in the semipermeable membrane is determined based on the amount of at least the aromatic polyfunctional amine and cellulose nanofibers used in the preparation of the sample, and the semipermeable membrane is A memory storing a calibration curve indicating the correspondence between the concentration of cellulose nanofibers and the infrared absorption spectrum, which is obtained by irradiating infrared rays from the side and analyzing the infrared absorption spectrum of the porous support in advance. Department and
an analysis unit that irradiates the semipermeable composite membrane to be analyzed with infrared rays from the semipermeable membrane side and analyzes the infrared absorption spectrum of the porous support;
a calculation unit that calculates the concentration of cellulose nanofibers in the semipermeable membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained by the analysis unit;
A measuring device comprising: Forming a semipermeable membrane containing cellulose nanofibers on a porous support made of polysulfone,
For a semipermeable composite membrane in which the semipermeable membrane is formed on the porous support, the concentration of the cellulose nanofibers in the semipermeable membrane is measured by the measuring method according to claim 1 or 2,
A method for producing a semipermeable composite membrane, comprising obtaining a semipermeable composite membrane having a predetermined concentration of cellulose nanofibers.

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